NAME

autoconf - autoconfiguration framework

SYNOPSIS

#include <sys/param.h>#include <sys/device.h>

DESCRIPTION

Autoconfiguration is the process of matching hardware devices with an ap-
propriate device driver. In its most basic form, autoconfiguration con-
sists of the recursive process of finding and attaching all devices on a
bus, including other busses.
The autoconfiguration framework supports direct configuration where the
bus driver can determine the devices present.
The autoconfiguration framework also supports indirect configuration
where the drivers must probe the bus looking for the presence of a dev-
ice. Direct configuration is preferred since it can find hardware regard-
less of the presence of proper drivers.
The autoconfiguration process occurs at system bootstrap and is driven by
a table generated from a "machine description" file by config(8). For a
description of the config(8) "device definition" language, see
files.conf(5).
Each device must have a name consisting of an alphanumeric string that
ends with a unit number. The unit number identifies an instance of the
driver. Device data structures are allocated dynamically during autocon-
figuration, giving a unique address for each instance.

INITIALIZATION

INDIRECT CONFIGURATION

void *
config_search(cfmatch_t func, struct device *parent, void *aux);
void *
config_rootsearch(cfmatch_t func, char *rootname, void *aux);
The config_search() function performs indirect configuration of physical
devices by iterating over all potential children, calling the given func-
tion func for each one.
The config_rootsearch() function finds the root device identified by the
string rootname, in a manner similar to config_search(), except that
there is no parent device. If func is NULL, config_search() applies each
child's match function instead. The argument parent is the pointer to the
parent's device structure. The given aux argument describes the device
that has been found and is simply passed on through func to the child.
config_search() returns a pointer to the best-matched child or NULL oth-
erwise.
The role of func is to call the match function for each device and call
config_attach() for any positive matches.
typedef int (*cfmatch_t)(struct device *parent, void *child, void *aux);
If func is NULL, then the parent should record the return value from
config_search() and call config_attach() itself.
Note that this function is designed so that it can be used to apply an
arbitrary function to all potential children. In this case callers may
choose to ignore the return value.

DIRECT CONFIGURATION

struct device *
config_found_sm(struct device *parent, void *aux, cfprint_t print,
cfmatch_t submatch);
struct device *
config_found(struct device *parent, void *aux, cfprint_t print);
struct device *
config_rootfound(char *rootname, void *aux);
The config_found_sm() function performs direct configuration on a physi-
cal device. config_found_sm() is called by the parent and in turn calls
the submatch function to call the match function as determined by the
configuration table. If submatch is NULL, the driver match functions are
called directly. The argument parent is the pointer to the parent's dev-
ice structure. The given aux argument describes the device that has been
found. The softc structure for the matched device will be allocated, and
the appropriate driver attach function will be called.
If the device is matched, the system prints the name of the child and
parent devices, and then calls the print function to produce additional
information if desired. If no driver takes a match, the same print func-
tion is called to complain. The print function is called with the aux ar-
gument and, if the matches failed, the full name (including unit number)
of the parent device, otherwise NULL.
typedef int (*cfprint_t)(void *aux, const char *parentname);
#define QUIET 0 /* print nothing */
#define UNCONF 1 /* print " not configured" */
#define UNSUPP 2 /* print " not supported" */
Two special strings, "not configured" and "unsupported" will be appended
automatically to non-driver reports if the return value is UNCONF or
UNSUPP respectively, otherwise the function should return the value
QUIET.
The config_found_sm() function returns a pointer to the attached device's
softc structure if the device is attached, NULL otherwise. Most callers
can ignore this value, since the system will already have printed a diag-
nostic.
The config_found() macro expands to config_found_sm(parent, aux, print,
submatch) with submatch set to NULL and is provided for compatibility
with older drivers.
The config_rootfound() function performs the same operation on the root
device identified by the rootname string.

ATTACHING AND DETACHING DEVICES

struct device *
config_attach(struct device *parent, void *cf, void *aux,
cfprint_t print);
intconfig_detach(struct device *dev, int flags);
The config_attach() function attaches a found device. Memory is allocated
for the softc structure and the driver's attach function is called ac-
cording to the configuration table. If successful, config_attach() re-
turns the softc. If unsuccessful, it returns NULL.
The config_detach() function is called by the parent to detach the child
device. The second argument flags contains detachment flags:
#define DETACH_FORCE 0x01 /* Force detachment; hardware gone */
#define DETACH_QUIET 0x02 /* Don't print a notice */
The config_detach() function returns zero if successful and an error code
otherwise. config_detach() is always called from process context, allow-
ing sleep(9) to be called while the device detaches itself (to deal with
processes which have a device open).
DEVICE ACTIVATION/DEACTIVATIONintconfig_activate(struct device *dev);
intconfig_deactivate(struct device *dev);
The config_activate() function is called by the parent to activate the
child device dev. It is called to activate resources and initialise other
kernel subsystems (such as the network subsystem). config_activate() is
called from interrupt context after the device has been attached.
The config_deactivate() function is called by the parent to deactivate
the child device dev. config_deactivate() is called from interrupt con-
text to immediately relinquish resources and notify dependent kernel sub-
systems that the device is about to be detached. At some later point,
config_detach() will be called to finalise the removal of the device.

DEFERRED CONFIGURATION

voidconfig_defer(struct device *dev, void (*func)(struct device *));
The config_defer() function is called by the child to defer the remainder
of its configuration until all its parent's devices have been attached.
At this point, the function func is called with the argument dev.

CODE REFERENCES

The autoconfiguration framework itself is implemented within the file
sys/kern/subr_autoconf.c. Data structures and function prototypes for the
framework are located in sys/sys/device.h.

SEE ALSO

HISTORY

Autoconfiguration first appeared in 4.1BSD. The autoconfiguration frame-
work was completely revised in 4.4BSD. The detach and activate/deactivate
interfaces appeared in NetBSD 1.5.
MirOS BSD #10-current August 25, 2002 2